Container



Nov. 21, 1950 A. H. WARTH 2,530,413

CONTAINER Filed Oct. 29, 1945 Patented Nov. 21, 1950 conranvcn Albin n.Warth, Baltimore, Md., assignor to Crown Cork & Seal Company, Inc., Md.,a corporation of New York Baltimore,

Application October 29, 1945, Serial No. 625,246

3 Claims. (Cl. 22064) This invention relates to containers particularlythose for packaging foods and beverages, in which a metallic surfacecomes into contact with the container contents. In addition, theinvention isconcerrfed with new alloys, metal coated with these newalloys and containers comprising such alloys.

Considerable difliculty has been encountered in the production ofcompletely satisfactory containers and packages for food and beverages,particularly those of a high acidic content such as citrus fruit juicesand the like. As is fully described in my co-pending application, SerialNo, 439,292,-filed April 16, 1942, and now abandoned, ordinary tin plateis not an entirely satisfactory material from which to fabricatecontainers for fruit juices because of the loss of aroma, flavor anddiscoloration of the contents upon ageing in the container. On the otherhand, the use of containers in which a metallic surface is exposed tothe container contents is advantageous in the packaging of acidic foodsand beverages if the metal surface exposed evolves a minute amount ofnascent hydrogen during storage of the packaged product. This advantageresides in the ability of the nascent hydrogen to maintain the packagedmaterial free from oxidation and other resulting changes in flavor anddiscoloration which accompany the oxidation processes. In this respect,containers having a metal surface exposed to the packaged product aresuperior to containers in which only non-metallic surfaces are exposedto the acidic packaged material, e. g., containers of glass or metalcontainers lined with enamel or organic resinous coatings.

Ordinarily, tin plate is the most common material used in thepreparation of food or beverage containers made wholly or partially ofmetal. However, this material is not entirely satisfactory for use inthe packaging of acidic foods and beverages because of excessivechemical attack upon the tin plate by the container contents. Variousmodifications of tin plate have been attempted in order to overcome thisdisability, e. g., the use of an alloy of tin with minor amounts ofsilver, as in my above mentioned patent application, for the productionof coated sheet metal to be employed in the production of thecontainers. However, even these improvements over the common tin platehave not resulted in the elimination of all of the deficienciesassociated with containers made from such coated metals. Thus, thesilver modified tin plate is subject to tarnishing and its corrosionresistance is not as high as is desirable.

. tainers as described above.

A principal object of this invention is to overcome all of thedeficiencies of the subject con- A further object is the provision ofcontainers having at least a portion of the surface exposed to thecontainer contents made from metal, said metal surface being highlyresistant to corrosion and oxidation.

A further object is the provision of plated sheet metal having a platingwhich is tougher than tin and containers fabricated from such platedmetal. Another object is the provision of plated metal from which foodand beverage containers may be produced which exhibit extremely goodsoldering characteristics. Further objects and the entire scope ofapplicability of the present invention will become apparent from thedetailed description given hereinafter.

These objects are accomplished according to the present invention by thepreparation of an alloy comprising tin, silver and indium, the platingof a base metal sheet with this alloy and the fabrication of containersfor foods and beverages from such alloys or coated metal sheets in whichany of the metal surfaces of the container exposed to the packagedmaterial is made of the alloy.

The success of this invention resides primarily in the discovery that analloy composed of a major proportion of tin and a minor proportion ofsilver and indium provides a sufllcient amount of nascent hydrogen uponcontact with acidic foods or beveragesto keep the true flavor ofcontainer contents during storage whil exhibiting an extremely gooddegree of chemical and corrosion resistance and attractive appearancewithout tarnishing or undergoing oxidation. The manner in which thisdiscovery is utilized may be stated as follows:

Sheet metal, such as black iron or steel of a gauge or thickness adaptedto permit fabrication of containers from the metal is coated with analloy comprising tin, silver and indium, such as an alloy of 93 to partsof tin, 0.1 to 3.5.palts of silver and 0.03 to 3.5 parts of indium. Thecoating of the metal sheet may be accomplished by a hot dippingprocedure, i. e., by dipping the sheet in the molten metal alloy; by anelectrolytic process, 1. e., plating the sheet metal in an electrolyticbath of an acid or alkaline nature containing silver, tin and indium inthe proper proportions to yield the desired coating; or by a vaporlyticprocess, i. e., by vaporizing thealloy in a vacuum chamber andcondensing the vapor upon the sheet metal plate. Moreover, acontainermay be fabricated from the uncoated base 3 metal plate and then coatedwith the alloy by any of the methods indicated above.

The alloy need not be used for making the entire surface of thecontainer, but is also satisfactory for use in the preparation ofcontainer closures having an overall or center-spot facing coated ormade from the alloy. Thus, a tin metal foil may be coated with the alloyfor production of container closures facings or thin foil may beprepared from the alloy. Such foil may be made in substantially the samemanner as is used to prepare tin metal foil, e. g., rolling. Thetin-silver-indium foil can be also mounted on paper material by means ofa thermoplastic adhesive, preferably by coating thepaper and then bymeans of heat and pressure wedded to the metal foil. The advantage isthat a somewhat thinner foil can be successfully used, namely, .001"foil or a trifle less, which can be mounted on a paper having .002"thickness or a trifle less. When using silver-tin-indium foil withoutpaper mounting, a thickness of at least 0.0015" is used, due to ruptureof thinner foils in the mechanical assembly of the spot or overallfacing on the disc or solid liner of the crown. Ordinary tin foil is notgenerally used with a thickness of less than .002" for Spot Crowns, butthe silver-tinindium foil is stronger and somewhat easier to handle anda lesser thickness may be satisfactory, but usually the.tin-silver-indium alloy foil is of a thickness in the neighborhood ofabout .002".

For the purpose of illustrating the invention I have shown in theaccompanying drawing a container and a cap coated with thesilver-tinindium alloy. It is to be understood that various types ofcontainers and caps as well as other articles employed for packagingfoods and beverages may be similarly lined or provided with exteriorcoating as described herein.

Referring to the drawings:

Figure 1 is an elevation partly in section of a can such as a sanitarytype can having a lining of the tin-silver-indium alloy.

Figure 2 is a sectional view of a can-end for use with the can of Figure1, similarly lined,

Figure 3 is a sectional view of a crown cap having its exterior surfacecoated with my improved alloy, and

Figure 4 is a sectional view of a crown cap having a cushion linercoated with a film of the tinsilver-indium alloy on its exposed surfacewhich may be in the form of an overall or center-spot facing.

The can ill shown in Figure 1 is provided with a seam II, which may besealed with either ordinary solder, with tin-silver-indium solder orsimilar materials. Alloys of tin with 3% to percent silver may be usedfor solders that require greater corrosion resistance than lead-tinsolders, or where it is desirable to eliminate the toxic lead. The alloylining is indicated at 13 and is coextensive with the interior wall ofthe container. The alloy may also be coated upon the exterior of the canto be coextensive therewith, and

I have found that it is highly receptive of the usual can decorationsand likewise imparts a bright finish.

The end shown in Figure 2 is the customary can end for sealing astandard sanitary can, as

shown in Figure 1, and has its inner or exposed surface coated with thealloy lining I 3. The exterior surface of the end may also be similarlyThe cap it shown in Figure 3 has a cushion liner l1 and has its exteriorsurface provided with an alloy coatin of tin-silver-indium alloy inaccordance with this invention. This coating, as just stated, willimpart a bright finish and will readily receive the lithograph or otherprinting decoration. The standard sanitary can shown in Figure 1 is madeof metal plate such as black iron or steel, previously coated with theimproved tin-silver-indium alloy and then folded or bent in the usualmanner into a can body by the customary body making machinery and theseam ll sealed in the regular way. The cap is likewise made from coatedplate, but instead of being bent to form, is stamped or drawn from thecoated sheet.

Referring to Figure 4, the crown cap is provided with a cushion liner i5 of paper board, cardboard, or other solid material and has secured toit exposed face a film It of the tinsilver-indium alloy as describedherein, e. g., tinsilver-indium alloy foil and constituting an overallor center-spot facing.

A more complete comprehension of the present invention may be had fromthe following illustrative example, in which all parts are by weight:

Example .This example illustrates the preparation of container of thesanitary can type from sheet metal prepared by hot dipping process.

A hot dipping bath is prepared by melting together 20 parts of silver,'7 parts of indium and 970 parts of tin containing 3 parts ofimpurities. The melting point of this resulting alloy is about 230 C.and bright finish black plate is readily coated with the alloy using anordinary dipping process, since the alloy has excellent flowingqualities and readily wets the sheet metal base.

The coated sheet metal is fabricated into a container of the sanitarycan type, such as that illustrated in Figure l, by the general canmaking procedure. It is found that this metal is particularly useful forthis purpose in view of the ease with which the can seams may besoldered.

Orange juice. is packaged in the resulting container. After storage fora considerable time, the

orange juice is found to possess substantially the same color, aroma andflavor which it had before packaging. Moreover, all of the surfaces ofthe container exposed to the atmosphere during storage retain a bright,untarnished appearance and the inner can surfaces show substantially nosigns of corrosion.

In another case, sheet metal was coated with ordinary tin and this tinplate was used to prepare containersand package orange juice. The orangejuice stored in this latter container for the same period of time as theformer, was found upon inspection to possess a distinctly changed aromaand flavor as compared to the orange juice originally packaged.

In still another case a container was made from sheet metal coated withan alloy of 97 parts of tin and 3 parts of silver. The chemicalresistance of this last container to the action of the packular type ofcontainer into which the alloy is to be fabricated and upon the type ofmetal to be packaged in the container. The most desirable.

alloys appear to be those in which the propor tion of tin to silver isbetween 1000 to 1 and 27- to 1 and in which the proportion of silver to1 indium in the alloy is between 1 to 1 and 7 to 1.

Particularly useful alloys are those comprising 93 to 100 parts of tin,0.1 to 3.5 parts of silver and 0.03 to 3.5 parts of indium. Anespecially useful alloy is composed of 97 parts of tin, 2 parts ofsilver and 0.7 part of indium.

This invention provides new and useful alloys which may be employed forapplications where high degrees of chemical resistance coupled with highdegrees of toughness are required. Although these alloys are, generallyuseiul for these purposes,-they are particularly applicable to theproduction of containers and container closures for packaging foods andbeverages, particularly those of an acidic nature.

I claim:

1. A sheet metal container having a coating on its wall 01' an alloyomposed of 93 to 100 parts of tin, 0.1 to 3.5 parts of silver and 0.03to 3.5 parts of indium, except for incidental impurities.

2. A container closure having on .its interior a coating composed of 93to 100 parts of tin, 0.1 to 3.5 parts of silver and 0.03 to 3.5 parts ofindium, except for incidental impurities.

3. An alloy composed of 93 to 100 parts of tin,

0.1;;to 3.5 parts of silver and 0.03 to 3.5 parts of indium, except forincidental impurities.

, ALBIN H. WARTH.

REFERENCES CITED Th iellowing references are of record in the flleifthls;patent:

': STATES PATENTS Number Name Date 135,028 Zimmer Jan. 21, 1873 250,326DeVllliers Nov. 29, 1881 1,437,641 Ferriere et al. Dec. 5, 19221,626,038 Ireland Apr. 26, 1927 1,632,309 Nitardy June 14, 19271,958,765 Perkins May 15, 1934 2,151,032 Scheller Mar. 21, 19392,157,933 Hensel et a1 May 19, 1939 2,241,789 Queneau et a1 May 13, 19412,364,713 Hensel Dec. 12, 1944 2,373,352 Smart Apr. 10, 1945 2,393,905Hensel Jan. 29, 1946 FOREIGN PATENTS Number Country Date 565,072 GreatBritain Oct. 25, 1944 Product Engineering, Oct. 1943, pages 630-632.

